Analytical methods for the quantitation of drugs are needed for the various phases of drug development. These methods must have specificity and sensitivity to quantitate drugs in dosage forms of the toxicology study, and in body fluids for human pharmacokinetic and efficacy studies. Chromatographic methods are most useful for this purpose. Drugs are extracted. The physical and chemical characteristics of each compound is evaluated in order to determine the suitable chromatography and detection. Volatile compounds are subjected to gas-liquid chromatography (GLC). Polar compounds are quantitated by high pressure liquid chromatography (HPLC). Extraction procedures for a variety of compounds were developed using a preferential solvents systems theory. The final methods were found to be suitable for a variety of both animals and humans.